Pmtiles js v4 (#499)

* pmtiles js v4: remove pmtiles spec v2 compatibility [#287]
* restructure ts files into src
* add tsup for building ESM/CJS and making types work in ESM
* bump fflate dependency
* update CHANGELOG for js 4.0.0

js/test/v3.test.ts

@@ -18,7 +18,7 @@ import {
   tileIdToZxy,
   tileTypeExt,
   zxyToTileId,
-} from "../index";
+} from "../src/index";
 
 class MockServer {
   etag?: string;